1. Field of the Invention
Example embodiments generally relate to a sheet supplier and an image forming apparatus incorporating the sheet supplier, and more particularly, to a sheet supplier for stably separating and conveying sheets and an image forming apparatus including the sheet supplier.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a sheet of recording media according to image data. Thus, for example, a sheet supplier loads a plurality of sheets and feeds the plurality of sheets one by one toward an image forming device. The image forming device forms an image on a sheet supplied from the sheet supplier.
The sheet supplier may include a friction member to separate an uppermost sheet from other sheets of the plurality of sheets loaded in the sheet supplier by friction. Specifically, the friction member, made of rubber having a high friction coefficient, pressingly contacts the uppermost sheet to separate the uppermost sheet from other sheets and conveys it as appropriate. One problem with such an arrangement is that the high friction coefficient of the friction member, which is necessary to feed the sheets to the image forming device in a stable manner, may deteriorate over time or according to environmental conditions, degrading feeding performance of the sheet supplier.
Further, when the image forming apparatus is used as a printer, it handles various types of recording media, such as plain paper, coated paper, and label paper. With recording media having a substantially small friction coefficient, sheets providing friction varying depending on temperature, or sheets absorbing moisture and adhering to each other, the friction member of the sheet supplier may not separate the uppermost sheet from other sheets properly.
Alternatively, the sheet supplier may include an endless dielectric belt, a charging member, and a discharging member to attract and separate the uppermost sheet from other sheets. Specifically, the endless dielectric belt is provided above the plurality of sheets loaded in the sheet supplier and moves in a sheet conveyance direction. The charging member applies alternating voltages to a surface of the endless dielectric belt to form an alternating charge pattern. The discharging member discharges the endless dielectric belt. The charge pattern generates an electric field on the endless dielectric belt to generate an attraction force for attracting the uppermost sheet.
However, under certain environmental conditions or due to resistance of the uppermost sheet, the attraction force for attracting the uppermost sheet may not be strong enough to separate the uppermost sheet from other sheets and feed the separated uppermost sheet. Consequently, the uppermost sheet may not be fed toward the image forming device.
Further, the attraction force for attracting the uppermost sheet may also act on other sheets under the uppermost sheet for a certain time period after the endless dielectric belt contacts the uppermost sheet. Consequently, other sheets may be fed simultaneously with the uppermost sheet. To address this, the sheet supplier may wait to separate the uppermost sheet from other sheets until the time period elapses after the endless dielectric belt contacts the uppermost sheet. However, such an expedient means that the sheet supplier cannot separate the uppermost sheet from other sheets quickly. As a result, the image forming apparatus cannot form an image on the uppermost sheet at the high speed required of contemporary image forming apparatuses.